Moderate and Universal Synthesis of Undoped Covalent Organic Framework Aerogels for Enhanced Iodine Uptake

The fabrication of hierarchically porous covalent organic framework (COF) aerogels is always challenging but of great significance in chemistry and materials science. The known COF aerogel preparation system is very limited and usually results in aerogel composite with low crystallinity. Herein, a universal and moderate synthetic strategy is presented for undoped COF aerogels through the catalysis of scandium trifluoromethanesulfonate. Due to the high catalytic activity of the scandium catalyst on aldimine condensation, densely distributed COF small crystal nuclei can be induced to be generated instantaneously under mild conditions, which leads to the immediate formation of crystalline COF gel within 5 min, whereas the traditional reaction system catalyzed by acetic acid is to form COF powder by slow accumulation of large two-dimensional lamellae. Thus, the COF morphology control based on the nucleation rate is realized. The hierarchically interconnected porous networks endow the obtained COF aerogels with enhanced adsorption performance for iodine, and the adsorption capacity can reach 8.15 g/g, which is among one of the highest iodine-sorbing values. This study provides a moderate and general method for the direct synthesis of undoped COF aerogels and has important significance for the processing and shaping of COF materials with prospective applications in efficient iodine uptake.